Fork- Lift Battey Equaliztion Charge Amps.

TexasDan

I am seriously considering a 24 volt battery bank made up of two 12 volt 500 pound folk lift batteries. (I would use two because moving two 500 lb. batteries sure beats trying to move one 1000 lb. battery.) One of the advantages I see is the ability to discharge a fork-lift battery 80% without damage which is how they are routinely managed by fork-lift battery chargers. That would provide a lot more usable amp hours than a traditional deep cycle multi-battery bank of the same amp-hour size. One issue however, is that some say that you will need the ability feed 40 amps into these big batteries for the required monthly equalization charge, which AC powered fork-lift battery chargers easily accomplish. Most home PV system charge controllers cannot push 40 amps. However, others say that it is not a matter of amps, but a matter of time. In other words, you may not be able to provide 8 hours of 40 amp charging like a AC fork-lift charger can, but you can equalize the massive 2 volt cells by using less amps over a much longer charge time. Any thoughts or experience with this? Thanks!

Cariboocoot

Re: Fork- Lift Battey Equaliztion Charge Amps.

There's more than one forum member who uses forklift batteries successfully. If you search for "forklift" you will probably come up with several threads about their experiences. Might need to use Google with the 'site' tag.

Yes, they are a bit different from a charging and discharging point of view. However Equalization is more of a Voltage matter than a current one, and PV's can push more than 40 Amps (standard MPPT controller is 60 Amps, and there are 80 Amp units as well).

A few of the threads:
http://forum.solar-electric.com/showthread.php?10595-charging-forklift-battery
http://forum.solar-electric.com/showthread.php?9013-forklift-battery-12-85-13-for-off-grid
http://forum.solar-electric.com/showthread.php?13718-why-not-use-a-forklift-battery
http://forum.solar-electric.com/showthread.php?5002-48-v-forklift-battery
http://forum.solar-electric.com/showthread.php?17255-using-a-forklift-battery
http://forum.solar-electric.com/showthread.php?8287-Forklift-Batteries

That should get you started. Always good to read up on something before plunging ahead!

vtmaps

Re: Fork- Lift Battey Equaliztion Charge Amps.

TexasDan wrote: »

One of the advantages I see is the ability to discharge a fork-lift battery 80% without damage which is how they are routinely managed by fork-lift battery chargers.

One caveat: In normal forklift use these batteries are discharged in an 8 hour shift and then immediately recharged. They don't spend a lot of time at low SOC. If it takes you several days to get down to 20% SOC and then a few more days to get recharged, you may find that you are sulfating your batteries.

Also, many forklift batteries have electrolyte recirculation systems that help mitigate the effects of stratification. Stratification contributes to sulfation in the lower parts of the plates. The combination of stratification with prolonged periods of low SOC may lead to disappointing results.

--vtMaps

Photowhit

Re: Fork- Lift Battey Equaliztion Charge Amps.

TexasDan wrote: »

I am seriously considering a 24 volt battery bank made up of two 12 volt 500 pound folk lift batteries....
...need the ability feed 40 amps into these big batteries for the required monthly equalization charge,
... Any thoughts or experience with this?

I'm one of those people with a 24 volt lift battery, it weighs right at 1100lbs and is 800amp hours, so for an 800 amp hour battery you need roughly 40 amps, minimum(5%) just to charge it properly...

Sounds like your trying to setup a system that won't work properly. Also note that forklift batteries typically are rated at an 8 hour discharge, so a battery rated as 500 amp hour (8 hour rate) will be 800 amp hour (20 hour rate).

FWIW - I don't think it draws much while equalizing, If I catch it during the monthly equalizing, I'll put a clamp meter on it. I have a 1700 watt array hooked up to mine, on a PWM CC so it only gets roughly 39 amps (1700/35vmp x .8 NOCT) but has minimal loads, in fact should cycle them more...lol

northerner

Re: Fork- Lift Battey Equaliztion Charge Amps.

I know someone with using fork lift batteries and they regularly go down to only 80% SOC, in order to get really long life out of the batteries (up to 20 years!). If you regularly discharge any lead acid battery to a 20 % SOC on a regular basis, you will reduce it's cycle life considerably.

I'm hoping new battery technology (ie not using lead acid) will be here soon, giving great DOD and much longer cycle life! This particular company, Aquion Energy, plans to start manufacturing batteries later this year, so there may be a product out soon.

http://forum.solar-electric.com/showthread.php?19079-Alternative-to-Lead-Acid-Batteries

Cariboocoot

Re: Fork- Lift Battey Equaliztion Charge Amps.

Don't hold your breath while you're waiting. :roll:

northerner

Re: Fork- Lift Battey Equaliztion Charge Amps.

Cariboocoot wrote: »

Don't hold your breath while you're waiting. :roll:

Don't worry, I won't.:p I have a battery bank that should give me over 5 years of use. Of course, that is an issue for someone needing batteries right away, but could also sway someones decision in how much to invest in lead acid.

stephendv

Re: Fork- Lift Battey Equaliztion Charge Amps.

All lead acid battery manuals that I've seen require a MAXIMUM limit of 5A/100Ah when the battery reaches the gassing voltage of 2.4V per cell. So I don't think having a lot of current available is really a necessity for EQ charging, it's more important for bulk charging so that you can reach EQ voltages during the day. If the battery is already at 80% SoC at the start of the day then you really don't need much current to bring it to EQ.

Here's a graph of the charging current for my 700Ah C5 48V forklift batt going through an EQ.

Attachment not found.

It peaks at about 27A, which is 3.8A/100Ah, because it started the day off with quite a high state of charge, so no trouble reaching EQ voltages.
vtmaps mentioned the electrolyte circulation systems, if you have a chance to order the batts with it installed, I'd really recommend it. It's the one thing I regret doing with mine.