Battery bank not holding charge--Please help!!

Re: Battery bank not holding charge--Please help!!

At this point, Meghan does not have any direct measurements of her loads (no battery monitor/load meters)... As I understand, it is a few lights, TV/DVR, and a propane heater (DC Fan?) in an RV.

It is a problem... However, the system seems to be discharging OK (nothing unusual for batteries and my guesstimated load of ~300 watts or so a couple hours a night).

The issue(s) appear to be--Unknown amount of charging with solar panels (some charging--details unknown). And a 6kW Honda Generator possibly charging the batteries with its 8 amp battery tender circuit instead of a real AC battery charger.

Installer is ready to "buy back" her system instead of trying to help fix/understand what is going on right now.

-Bill

Re: Battery bank not holding charge--Please help!!

Meghan,

You really need to measure your DC load current (and charging current).

The best way is with a $160+ Battery Monitor--The cheap way is with something similar to this $60 DC (and AC) current clamp meter.

The clamp current meter is very safe and easy to use... Plus it is a good diagnostic tool you can move around your system and see what is going on.

At this point, either will work for you--But if you want to avoid dumping more money--the Clamp Meter is probably a bit more useful and 1/2 or 1/3rd the cost. Its only cost to operate is a pair of AAA batteries (should last many hours of measurements).

-Bill

Re: Battery bank not holding charge--Please help!!

I don't have much to add to what Marc/Cariboocoot said other than you might try to find another solar RE installer in your area and get a review/quote from them. You know more today than last month and can ask them to review your setup and have them tell you what they would do to fix the problems/install new.

With the clamp meter, you can now measure how much current is going into the battery bank when charging with solar and your generator. And you can measure your loads too.

Very roughly, if you draw 10 amps for 5 hours, that is 10a*5h=50AH consumed. And it will take ~110% of that (for AGM) to restore that energy used or 1.1*50AH=55AH to properly recharge the battery bank. So, if you solar averages 30 amps charging, it will take ~55AH/30A=1.8hours plus ~2 hours to fully recharge (as batteries approach full charge, the current drops off).

Your batteries are in parallel--So you will have 100% of the current in one wire coming/going to the batteries, and if you have two parallel strings, you will have 1/2 the current going to each battery. If one battery is handling most of the current (charge/discharge) and the other is not, then there is a wiring/battery problem.

[FONT=Fixedsys]
         100%          50%
Positive=====+===|-|-|======+
             |              |
             |         50%  |  100%
             +===[/FONT][FONT=Fixedsys]|-|-|======+=======negative
               batteries
[/FONT] 

The DC Clamp meter... Set the meter to DC current. Set the Range to 40 amps (or 400 amps). Push the Zero Button to get it to zero and then clamp it over the wire you wish to measure current. Note that the DC meter will read + or - depending on the direction of current flow (or if you flip the meter over).

Do several measurements over the day to see what your average charging current is. And again at night, first with nothing turned on (no load), and then each load one at a time so you know how much each draws.

Then you can measure with your "average" loads turned on (lights, TV, etc.) and figure out how long you can use the power at night.

-Bill

Re: Battery bank not holding charge--Please help!!

Meghan,

I will try to answer a few of your questions:

meghammock wrote: »

I love this.. Feels like school that's worth attending:)

Cariboocoot:--Why would the 173w GE panels not be the best for this? (not arguing; just want to know:) )

If I have the correct GE panels, their Max. Power Voltage (Vmp)=25.1volts...

With a PWM charge controller (simpler, less expensive to make), they are best used with Vmp~17.5volts on a "12 volt" battery bank.

• 17.5 volts / 25.1 volts = 0.70 = 70% efficient vs the "right panel Vmp"

It gets into electronics a bit more than you are probably ready for... But basically, the solar panel is running around 15-17 volt output when charging the battery bank instead of 25.1 volts or so... Remembering Power=Voltage*Current; when Voltage drops and current remains the same (the way a solar panel works), then the Power drops too.

With a MPPT type charge controller (2-3x more expensive), they have a switch mode power supply that allows the MPPT controller to efficiently "down convert" the High Voltage/Low Current of the solar array into the Low Voltage/High Current for the battery bank... For example, a MPPT controller's math would look like:

• Vmp*Imp (panel) = Vbatt*Ibatt (battery)
• 25.1 volts * 6.9 amps (solar panel) = 14.5 volts * 11.94 amps (battery bank) = 173 watts charging battery bank

Where for the GE panel on a PWM power supply:

• Vbatt*Imp = 14.5 volts * 6.9 amps = 105 watts charging battery

I have simplified the above a bit--There are about 5% losses with the MPPT charge controller.... Plus hot solar panels do not have Vmp, but a reduced Vmp-hot which reduces MPPT actual output.

But it is a good start at understanding the differnence.

The solution would be to install a MPPT charge controller or to replace the GE panels with other panels that have Vmp=~17.5 volts or so...

But it also depends on money... It is possible that the GE 173 watts panels are less expensive than 120 watt Vmp=17.6 volt solar panels... So, it could still make economic sense to get the GE panels over some other 17.6 volt panels instead.

However, most people would look at the 173 watt panels and wonder why they only get "121 watts" worth of power from them--and the fact they saved money with a PWM charge controller may not make sense (leaving power on the table).

--I don't think the batteries are too far gone; I definitely think it's got to do with how the loads are coming in and out..

Don't know--but they may still be good.

--What is it about the PWM type controller that makes it not compatible/so bad? In contrast, what makes the latter so compatible/good?

See above--PWM controllers are quite a bit less expensive... For smaller systems (under 400 watts) a PWM controller may make more sense.

For systems over 800 watts, MPPT charge controllers are usually better / easier to install and can use less expensive solar panels (those that don't have Vmp=17.6 volts).

--Yeah, I definitely have plans to save up and get a Magnum truesine inverter at some point.. You're right..

In the long run, True Sine Wave inverters are a better choice (even if horrendously expensive).

For your system, you may want to run the small loads with a MorningStar TSW 300 watt 12 volt inverter. It is actually a very nice unit, and can be put in "search mode" so that uses less power when nothing is turned on (sleep mode).

Use the big MSW inverter for power tools and such. Use the smaller TSW for electronics... Many times having two different sized inverters (and generators) makes good sense. Use the smaller inverter/generators most of the time (and save energy). Use the big inverter/generator when lots of power is needed for power tools, running the wash, etc.

--Is it possible for me to trim the wiring down to make it more manageable/less wasteful??

Yes--But you want to make sure you have the correct hardware (bolt on connectors, crimp connectors/tools, etc.) before you start.

--YES, I definitely feel like we came up with MANY more answers than those jokers did.. They have been even slimier lately.. UGH!

Ouch!

--As far as quality goes, sounds like it'd be wiser to dive in and get an MPPT style controller than switch the panel type, correct? I'd rather have good stuff that's going to LAST and work well, after all..

Either can be a good solution (sell panels back and buy correct ones; or change over to MPPT charge controller).

One decision point may be based on the question "do you want to add more solar panels in the future?". And are "GE 173 Watt panels still available for a good price".

Basically, you have to match solar panels to charge controller type and battery bank voltage.

The downside with the >100 watt solar panels being a lot less expensive is that they do not standarize on Vmp/Imp ratings anymore (Vmp had to be standard to work with PWM controllers and 12/24/48 volt battery banks).

Today, with MPPT controllers, as long as the current panels match--the MPPT will take care of matching Vmp/Imp of the array to the battery bank voltage (at 95% efficiency).

--They are offering to pay back the entire contracted amount: $6,414. When I did the math, I believe they gave us a bogus number on how much all the complonents cost together.. I couldn't find a difinitive price on the panels, but everything else was TEENY when compared to the final price!! I'm temped to let them buy it back, then see what ya'll have to say about what parts and components to buy, eh?

I would be tempted to return the product... They have yet to give you a working/usable system yet.

Do you have a plan "B" yet?

• get a smaller Honda eu2000i or eu1000i (1,600 watt or 900 watt) genset to get you by for a few months
• locate "somebody" that can install the system correctly?

(I certainly don't mind keeping what we've got right now for the time being as our "maiden voyage" system, if we can reuse the panels and whatever else later on.. I plan on replacing the inverter and controller FOR SURE though, and most likely, the batteries before we "upgrade" our system when we have our house built..)

You can probably make this system work better... But you may be able to do better with your $6k money back in your pocket and start over. If you can take the hit without your battery power (which has not been working well for you yet).

BB.:
I did try getting in touch with another solar contractor around here.. Good gracious, they seem to be useless around here! You'd think they'd be itching for the business considering people utilizing solar are a precious commodity around here, but I guess not! I guess it's just like ya'll said.. Either a quick buck, or just side cash when convenient:(

Try looking for Boat Builders/Repair companies in the area. They may not do solar, but they can get the rest of the system installed and working well for you (including the generator portion).

Or, perhaps a good RV company--Ask to see their work/talk to a customer that had them rewire their RV.

Frankly, if they get the battery/AC charging system/inverter setup working well for you--Doing the Solar PV array + charge controller is pretty much a piece of cake.

From the looks of your diagram (and the print-out you gave me that I was reading on the other day) that is our problem though.. The load is being put in AND taken from the same series!

It is OK (and probably the right thing to do) to take the load and apply the charge in the same location. The +/- bus bar/common connection points are chosen to ensure that the parallel battery strings are properly sharing current.

In your case, you may have a secondary problem with current sharing in the string--but unless there is a broken cable/open/dirty connection, I don't think it is your problem just yet.

We recently tried to ask them about that, and they are no longer trying to answer questions or help us fix it. Would there be any harm in me switching how the loads are connected to the bank? I marked on the bank picture how the loads are fed so ya'll could see more easily in the jumble, and "named" the batteries for easier reference. I was wondering if I could connect the Inverter wires to the 1--2 series instead of Inverter AND Controller wires being on the 3--4 series?? (Though I'm curious why there are 2 like that in the first place??)

I am not quite sure I understand your diagram/question--so I don't feel confident giving you an answer just yet... At this point, without further data, we may be just rearranging the deck chairs. Better to understand and fix the other issues first.

Cool.. Are all places on wires safe to use the c-clamp device? And wheeeere exactly do I check to find out how many amps are being used? Would that be within the camper? I think that's where the "company" checked the load the camper was using..

The current clamp itself is safe--I believe it is rated for use with up to 600 VAC--Way more voltage than you will see.

And the current clamp is insulated so it cannot short anything out. Use the 40.00 amp scale unless you need the 400 amp scale (lots of charging current). It will not damage anything if you have the wrong scale.

Photowhit:
I'm not sure about the on-board battery charger, but the single battery the camper came with doesn't seem to be connected to one.. Any ideas where that might be?? I can certainly look tonight.. Good thought! Would that need to be disconnected?

Most RV's come with an "AC Power Converter" -- Basically some sort of 12 volt battery charger system that plugs into 120 VAC power. They are intended to both run your DC loads when you are parked at a campsite when you have AC power, and to recharge the battery bank when you get home from "dry camping".

Trace the AC wiring from your breaker panel... Generally you will find the AC Converter in the back of one of your cabinets or behind a drawer (pull out the bottom draws under you counters). Or possibly behind an access panel from outside the RV. (I am not an RV guy).

If you find your AC converter--It would probably make sense to reconnect it to your battery bank and run the AC cord from the converter back to your 6.5kW AC genset. That will make a good dent in properly recharging your battery bank and a better use of your generator fuel.

I'm pretty sure the heat is strictly propane, other than the blower fan on it.. I had my hubby check on that, but it's certainly worth checking again!!

Changing/using a propane heater that does not need a fan can save you battery power... You can use the DC Clamp meter to measure the fan current (amps) and estimate how many hours per night the fan runs (1 hour, 3 hours, etc...)... If the fan does not run for hours per night--it may be OK to leave as is for now.

But, in the end, you do have to account for all of your loads and how much solar/genset recharging power you have. It is a balancing act (power out/power in/generator fuel in/money out).

-Bill

Re: Battery bank not holding charge--Please help!!

Be aware, there are two models of TS-60 controllers from MorningStar:

• TriStar 60 amp 12, 24, 48 volt PWM solar charge controller
• Morningstar TriStar 60 amp MPPT solar charge controller

One is PWM and the other is MPPT (and they look pretty similar, I think). Of course, one is under $200 and the other is over $500--So that should give you a hint.

At this point, you have the choice to fill your battery box with "appropreate" amount of batteries and design the charging system for that amount.

The other option is to measure your loads, design the battery bank to support the loads, and then design the solar/generator systems to support that size battery bank/load.

At this point, if you are going to go with fla's (Flooded Lead Acid?) batteries that fits your power box--You might try an inexpensive set first (i.e., good quality 6 volt "golf cart" type batteries) and see how well that supports you for the next 3 years +/-... After you blow through the first set and have real measurements and experiences, you can then look at optimizing the battery bank for the next time.

Even if you decide you need 2x more batteries in the near future--you can add more FLA golf cart batteries for now for not much more money and balance out the system to meet your needs.

From what I have seen, all else being equal (a big IF), If you pay 2x for your battery bank (2x in quality, or 2x in bank size), the batteries will last ~2x longer...

Spending a lot on your starter bank and making mistakes on setting up/running can be expensive.

Our host does sell batteries, but give how much they cost to ship, looking for a local battery distributor may save you some money--and give you a local source for information, battery cables, etc. (and recommendations for somebody that knows how to configure a battery system).

Also, unless you have large power needs or cannot pull start a genset--I would look at getting a Honda eu2000i for ~$920 or so shipped to your door/property... And set it up to siphon from a 5 gallon gas can (you can get a kit, or buy an extra gas cap and make your own).

Otherwise, generally a small as possible, quiet, electric start inverter genset (Honda, Yamaha, possibly a used RV genest from wrecker, etc.).

-Bill