Need charger suggestions for 800 AH @ 12 volt Battery Bank

unseenone

OK, so I have a bank of batteries running series parallel. There are four 6 volt 400 amp hour batteries. So they are operating at 12v with an 800 amp hour storage. The batteries are new, so out an abundance of caution, I would like to get a proper battery charger so I don't habitually undercharge them. The 6 volt battery calls for a 60amp charge, with a max charge of 80amps. From what I am reading here, I probably would have been better off with 2 volt batteries and a 24 volt system. All things being what they are I will do this in the future.

For now, out of what you're offering, what charging system would you suggest, from your offerings. My main purpose is to ensure the batteries get a proper charge.

I know on the solar side I need more panels, and increased amperage.

BB.

Re: Charge battery bank by splitting it up with multiple chargers?

Welcome to the forum Unseenone.

For your 12 volt setup--The charger the mfg. would be recommending then would be 2x60-80 amps or 120-160 amps for your 800 AH battery bank.

In reality, for general use, you can go with 5-13% or so, and ~10% being a good value (Goldilocks principle, not too big/not too small). And, depending on type of battery (GEL, AGM, flooded cell)--You can push the charging envelope one way or the other a bit too.

80 amps at 12 volts is still a hefty battery charger (not cheap, and not a lot of options out there for stand-alone chargers).

I like to design "balanced" systems... Match the battery bank to the loads, and then match the charging system to the battery bank (and how quickly you need to recharge the loads).

A 800 AH at 12 volt system (and I agree that 24 volts or higher is probably a better choice) with 2 days of storage and 50% maximum discharge would give you around:

800 AH * 12 volts * 1/2 days * 0.50 max discharge * 0.85 inverter eff = 2,040 WH per day

That is a good size system for a small cabin... And just about the limit for running a standard EnergyStar full size/efficient refrigerator.

One of the things to look at is your AC loads. There are some nice 120 VAC AC inverter-chargers -- The combined unit gives you nice functions (such as automatic UPS functions) plus the internal charger can be programmed for use with smaller gensets (a 1.6-3.0 kWH Honda or Yamaha inverter-generator is very quiet and pretty fuel efficient when operated at lighter loads (a few loads in the house/cabin with the AC power as failed--Or even as a bad weather backup generator).

So, tell us a bit more about your battery bank and your overall power requirements--On grid/emergency backup, storing the batteries for a few months then installing in a summer cabin, etc.

You are correcct to worry about worry about the batteries--At best flooded cell batteries can sit for ~1-3 months without day or so of recharging--If they sit longer unused/uncharged, they will sulfate and you end up with a load for the recyclers/cores for the next system.

Also, I will move this to your own thread... Will help keep the Q&A focused on your requirements.

-Bill

unseenone

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

The main purpose was to learn more about solar, and the exercise was to setup for use in emergencies with the potential to move the system into an RV later. Currently we're on the grid.

I wish I have found you folks sooner, but I'm glad I did. This is not a "light" system, but it is put together so it can be broken down and moved as quickly as one can move 123lb batteries. I guess I failed to mention these are AGM batteries. As far as sitting time, depending on the time of year, let's figure 3 months in TX. I can set it up, so it's always on, which increase wear & tear, or I can park it until it's needed. For now, it's running.

When I do this again, I would plan for a 24/48 volt system to begin with for the house, For the RV, it would be 12 or 24, most likely 24 because the wire size & amperage advantages. Of course that's another conversation, and I'm not in that boat yet, speaking of boats... well I digress.

I am good on storage capacity with the current setup. It would probably not work well to try and expand this system to 24 volts, and I haven't considered the 12v only components yet for that configuration. While it is too small to do a grid tie, it is OK for emergencies.

My intention will be to use this to keep the 7cu ft non-defrost freezer on short term in the event of a power failure. The freezer is kept as full as possible with frozen water bottles in it. This will require an inverter, which is also very wasteful. I picked up a new 3600w commercial inverter. Again, way over specification for what is needed. The inverter is about 88% efficient. I don't need it badly, but if something comes up, it's there. The optimistic power use for the freezer is 282kwh annually. It's a power sucker for sure. Worst case would be to transfer critical foods to the DC fridge/freezers.

Additional loads I will add;
2 12/24 volt DC fridges, which will draw 35 amp hours each a day.
1 Ham Radio, power usage depends on the duty cycle, something like @ 21amps x 4 hours and 20 hours at 600ma to 1amp.
2 3 watt LED 12v Lights

Panel wise -- I need a ground or non penetrating roof mount. I'm fascinated with solar tracking, but it's way overpriced. I'm using 250w 60 cell panels, presently I have two, and I will be adding more, I didn't want to go crazy to start so I picked up two 250 watt panels. I can add two more at 24 volts or 8 at 48 volts. This should get peoples attention when you are considering panels and their output voltages.

I've been testing, and have one 12v fridge connected 24x7. The voltage drop by morning is 0. Once the sun goes down, it settles to it's 12.8 volts and in the morning it is still at 12.8 volts.

While I do not anticipate deeply discharging the batteries, I want to take care of them, so I think a charger would be a good plan. So would a generator, I agree.

Photowhit

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

You do understand, that if you want a 24v system, there is no reason you can't make one string of these 6v batteries?

Voltage is a poor way to estimate power use, a shunt based battery monitor might be suggested....

unseenone

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

I'm not sure what your talking about. I was talking about the advantages of 12 vs 24 vs 48 volts in terms of lower amperage at higher voltages.

If I run a 24 or 48 volt system, I still need provisions for my 12v only gear. I have plenty of storage for my current setup. I think your suggestion is a good idea if when I switch, I just think it will add a level of complexity I don't yet need.

I would love to hear more about the shunt based battery monitor, but it may be overkill but might be fun to play with. My main point for posting was about chargers, which is again going to depend on the voltage I settle on, which is currently 12.

Obviously power is used, although the voltage doesn't drop, anyone would know that. According to the battery manufacturer they considered the battery full at that voltage, and so on, as AGM voltage charts go.

Photowhit

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

unseenone wrote: »

From what I am reading here, I probably would have been better off with 2 volt batteries and a 24 volt system. All things being what they are I will do this in the future.

Changing later means changing much/most of your system. If you wanted 400Ah at 24v you would be fine now. All lead acid battery banks are made up of 2v cells, if they string 3 together and put them in one box, it still has 3 cells, but a 'battery' of 3.

Shunt based battery monitors

unseenone

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

I'm having a hard time getting used to the replies being on the top, I thought only the Australians did that.

OK, so let's say I make the leap into 24 volt now, what would you suggest for my 12 volt only gear? I'm sure you can get there, but I'd like to hear your suggestions. I could always add 4 more batteries to increase my storage.

Photowhit

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

You can switch the way you view the forum, I seem to have switched back and forth a couple times, I think it's under your account...

I would guess your primarily worried about the ham equipment? I'm not sure, A/C and transform back? I ran DC into my place for a short while and found AC worked better for me on pretty much every thing, even having to transform it back to DC for a TV/Video tape player, but as you might suspect at that reference it's been a while.

Adding batteries later, mixing new with old is generally a bad idea. Generally better to be under powered until you kill off your first set...

BB.

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

I have set your display to do oldest first--You can go to the "Settings" (upper right) and change some basic forum behaviour.

-Bill

unseenone

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

Thanks for fixing my settings, duh, I'm a mod on another forum I set up, I should have thought about that.

Yes, you are right the ham stuff. The think to remember is, it's very inefficient to convert DC to AC back to DC. I saw another thread on the subject of keeping 12v with a 24v system. It looks like there is a device that can be used, but it will also waste some power. There is one mentioned by Vanner, as well as a smaller one NAWS offers.

The other issue with HAM stuff, is going to be keeping the noise out of the system. It should be possible, I have not yet begin fiddling with it to see how it is yet.

My batteries are brand new, so if I am going to do this, I should do it now, no point in waiting 10 years (I hope).

BB.

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

What radio(s) do you have?

Many require ~13.8 volts for full rated transmit power (also, are you looking at 10-50 watts, or 1,000+ watts transmit power, and ~2x times input power). You can get DC to DC converters--But you end up with similar losses as going with an AC inverter.

Going with 24 volts and a 120 VAC inverter to power most of your loads takes the wide range of an off grid DC battery bank (roughly 10.5 to 14.5 volts for AGM--15 volts or higher for flooded cell). Let the AC inverter manage the wide range DC input.

If you still are interested in 12 VDC--Yes, there are the DC to DC converters--But there are also several other options.

A common one is to get a 12 volt battery to power your (smaller) loads, and use a MPPT solar charge controller to charge the 12 volt battery bank (or other DC to DC charge controller).

And there is a class of DC to DC converters that is used on RV conversions (I believe Vanner is one of these vendors)... 12 Volts for house power and 24 volts for engine power... An isolated DC to DC converter that connects the High 12 volt bank to the low 12 volt bank... The DC converter is bi-directional and will keep the two 12 volt sub-string voltages identical (over time). This allows you to "tap" the lower 12 volt bank and keep the whole 24 volt bank in balance.

Complexity, efficiency, and cost wise, the above are not much different than just powering everything from 120 VAC inverter.

With AGM and using the batteries for "backup" power (at least for now)--As long as you have grid power you can use an ~40 amp battery charger to keep the batteries charged between uses. Also, this type of charger is small enough to use on a Honda eu2000i (1,600 watt) inverter generator. If you want more charging current, you would need a larger genset (and larger battery charger) or a configurable battery charger (typically an inverter-charger--Configurable AC battery chargers are bit on the rare side so far).

Otherwise, to power your refrigerator--Even small ones usually need around 1,200-1,500 watt AC inverter to manage the starting loads. Inverters that are rated to 600 Watts maximum are not usually "stiff enough" to start a typical refrigeration compressor.

-Bill

unseenone

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

Thanks

The radio is Yaesu 857D. 21-22 amps at full duty cycle, wired in a 30amp circuit. That would be at full power. You are correct, 13.8 volts Nominal +- 15% So out of the gate, I am about 1 volt low. That voltage will change depending on the temperature. During the day, when power is being produced it would not be as big of an issue.

niel

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

unseenone,
you most likely have a power supply that you could plug into an ac outlet except it's power is from an inverter running from high dc battery voltages like 48v. keep your 12v stuff on the power supply as you would if you had the grid as that's the easiest way for you to go about it. this added draw to the inverter batteries means you must increase your capacity to account for all of the loads plus ham.

you can go to a 12v battery and just charge it either with solar or a battery charger plugged into the big inverters output. this adds more cost, but would work for limited times with only that battery up to 1/2 of the ah capacity of the battery. i don't see the need for this duplication, but you can do it. if you find your noise levels unacceptable then the battery operation may suit you better and you can charge the battery up with a charger after your qso is done.

jonr

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

Is it true that if you run a 24V battery bank (say two 12V batteries in series), you can use independent chargers on each? For example, a panel and a 12V charge controller dedicated to each battery with no shared ground between them? Yet still pull power out at 24V (and if needed, 12V by pulling from just one battery).

Cariboocoot

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

jonr wrote: »

Is it true that if you run a 24V battery bank (say two 12V batteries in series), you can use independent chargers on each? For example, a panel and a 12V charge controller dedicated to each battery with no shared ground between them? Yet still pull power out at 24V (and if needed, 12V by pulling from just one battery).

Yes, but it's not the best idea because the chargers even if identical will not be exactly matched. One battery inevitably will get more charging than the other, resulting in unequal SOC between them.

If you pull 12 Volts off one half that imbalance will increase because it will be happening on discharge as well as charge.

unseenone

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

BB. wrote: »

<snip>

And there is a class of DC to DC converters that is used on RV conversions (I believe Vanner is one of these vendors)... 12 Volts for house power and 24 volts for engine power... An isolated DC to DC converter that connects the High 12 volt bank to the low 12 volt bank... The DC converter is bi-directional and will keep the two 12 volt sub-string voltages identical (over time). This allows you to "tap" the lower 12 volt bank and keep the whole 24 volt bank in balance.

<snip>
With AGM and using the batteries for "backup" power (at least for now)--As long as you have grid power you can use an ~40 amp battery charger to keep the batteries charged between uses. Also, this type of charger is small enough to use on a Honda eu2000i (1,600 watt) inverter generator. If you want more charging current, you would need a larger genset (and larger battery charger) or a configurable battery charger (typically an inverter-charger--Configurable AC battery chargers are bit on the rare side so far).

Otherwise, to power your refrigerator--Even small ones usually need around 1,200-1,500 watt AC inverter to manage the starting loads. Inverters that are rated to 600 Watts maximum are not usually "stiff enough" to start a typical refrigeration compressor.

-Bill

Should I call Vanner directly for advice or is this something the gang here can get a quote on, I can sort the models. I think I'm interested a quote both ways, DC-DC Converter in the 50amp range, or the Equalizer in the 50-100 amp range. The main concern is not introducing noise or interference in the system for communications. I am sure they will have opinions on this.

Their web site is a little difficult to navigate, but I think along these lines would work.

90-50A Converter
http://www.vanner.com/manuals/90-50A.pdf

81-60CAN Equalizer
http://www.vanner.com/manuals/EQUALIZER-81-CAN-SERIES.pdf


Once I've got this part sorted, I will know which charger I need, 12 or 24 volt.

BB.

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

How serious are you about electrical noise.... Solar, DC switching supplies, etc. are pretty notorious for causing noise (AM band, short wave, etc.).

Moving the antenna(s) as far as you can from the solar array/switching power supplies can help a lot. Checking that the supplies/charge controllers meet FCC Class A or Class B (B is better) can help. I don't see how--But many solar equipment designers believe that their equipment does not need to meet Class A/B requirements and do not work very hard at reducing radio emissions.

DC Common Mode noise is more difficult to filter out because the usual magnetic/inductive filters saturate at fairly low currents (a few amps?).

We have multiple threads here about reducing emmisions and it is not very successful many times.

Placing your wiring in metal conduit, filter caps next to I/O on power equipment can help...

-Bill

unseenone

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

Hi BB;

I have no issues with noise so far, the only noise that will be introduced is based on the direction I go with the 24 volt conversion, and the 12 volt converter or equalizer. I have a mobile configuration I just setup, I need a solar panel for it and a mounting scheme. I have tested it, and it is quiet as a mount, no problems. I guess you could say, I would like to be serious about electrical noise, and avoid introducing anything I cannot filter out.

What are you suggesting with regards to a direction?

Here is the mobile setup.

BB.

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

If you are not having any issues--Then continue on. Lower power systems tend to be quieter--But, a badly designed low power controller can still send out lots of RF.

-Bill

unseenone

Re: Need charger suggestions for 800 AH @ 12 volt Battery Bank

We got a little of track I guess. The original idea, was to pick a charger for a 12v system. That led to a discussion on switching to 24 volts, which let to a discussion on inverters, converters and equalizers, well, mainly suggestions, which led to a mentioning RF, or the potential RF interference with these devices but no conclusions yet.

Does anyone have any first hand experience with converters or equalizers, Vanner or otherwise.