Electric forklift replace battery with EV battery

[mihaihotca]

Hi there, I would be curious if I can find someone that has done a conversion or would know i theory if it would be suitable to replace a bad forklift battery with one from an EV.
The forklift is rather old and used a 48v 400ah lead acid battery. I’ve had it lying around for some time and now I want to either make it run or scrap it. Replacing the battery pack is too expensive and it’s still the same technology of lead acid, I would maybe use it for the shop around 1-2 times per month to unload light stuff so not too feasable to invest in the traditional battery. I saw that new models are using lithium tehnology and I had to question myself if I can use a used battery pack from an electric vehicle, they have a fair price and at least they have better characteristic than lead acid for life time/weight etc.
So my question is would this be a simple job as findig an 48v battery pack and simply connecting it to the forklift? I understand that I would have to change the charger and I also know that the packs come with some battery system management on them.

 

[dalmatiangirl61]

IIRC electric car batteries are configured for higher than 48v, you would have to reconfigure the cells. EV batteries are also lighter, and most electric forklifts use the battery as ballast, so you would be reducing lifting capacity unless you also included some lead or cement blocks. Probably easier, cheaper, quicker to just use 4 - 12v batteries in series which would be adequate for occasional use.

 

[cyanidekid]

yup, as d61 said, it is actually dangerous to replace the stock lead acid batts with lighter ones, L-ion or not. they are an essential counterweight.

 

[crickets]

There are companies that make retrofit batteries for forklifts, for example https://www.triathlon-batteries.com/.

If building the battery yourself, there are some design considerations including what other posters mentioned regarding the counter-weights. Triathlon batteries for example contain steel plates in them to bring the total assembly weight to required 2000lb or so.

So anyway, doing it yourself it is best is to use something like Nissan Leaf modules due to their size. Will need a configuration of 7 in series, which is 14 cells in series (each module has two pairs of cells in series). To account for the current draw (most warehouse electrics are fused at 400A) battery needs to handle at least that much continuously, which means the minimum would be 14 modules total (132Ah or 6.8kWh). Such assembly would then be around 130lb, so need to add 1900lb or so of ballast.

In addition to the battery modules will need a Battery Management System with the capability to manage 14 cells and to drive external charge and discharge contactors (48v / 400A min), and separate 400A fuse. Finally will need a charger suitable for this battery configuration - can't use the stock forklift charger.

If this thread goes any further, I can provide the specifics on the battery building - done it a few times, including for running an electric forklift

 

[johansen]

If you really only need 14 cells, you can buy an active bms for like 25$. It will only be good for 1 amp, but they are passive, they only care about the difference in voltage. You can spend more on a more capable unit or put a few of the smaller units in parallel.

if the batteries are matched well, and if you have competent workers who can watch a volt meter and plug the machine in if the voltage drops to some value, then you do not need to spend 500 bucks on a 400 amp rated 48v BMS..

you do need a battery charger configured properly to shut off at a safe maximum voltage.

 

[crickets]

If you really only need 14 cells, you can buy an active bms for like 25$. It will only be good for 1 amp, but they are passive, they only care about the difference in voltage. You can spend more on a more capable unit or put a few of the smaller units in parallel.

A BMS for $25 likely wouldn't work. First of all, those boards are designed to pass the load current through the onboard transistors, which is what limits their amperage. Instead for a high current application we want a BMS that monitors and balances cells, but the load and charging currents go directly to the battery via contactor(s) that would be controlled by the BMS. So the current rating is then not a product of the BMS size, but rather the contactor size. This is the standard approach for EV batteries, as opposed to ebikes and power tools.

Second problem with many of those cheap boards is that voltages in them are not programmable. They're typically set for 4.25 or 4.20 as the over-voltage condition. It is not a good idea to charge the cells that high.

if the batteries are matched well, and if you have competent workers who can watch a volt meter and plug the machine in if the voltage drops to some value, then you do not need to spend 500 bucks on a 400 amp rated 48v BMS..

Yes, and also he can burn down the shop. Decent BMS that will work for this application will run $250-300. When buying salvaged cells online there is no guarantee they came from the same EV pack and are closely matched. Even in the same pack they often degrade differently due to uneven cooling.

you do need a battery charger configured properly to shut off at a safe maximum voltage.

Charging stops automatically once the voltage is equalized between the charger and the battery. However, charger only understands the total pack voltage and not the voltage at the cell level. For that reason BMS has to be capable of forcefully disconnecting the charger to prevent cell overvoltage.

 

[johansen]

The active bms i am speaking of is just a series of buck converters that equalize the cell voltage, without wasting the difference in energy, in resistors. They dont care what the battery voltage is, only the difference in one cell to another. There are several on the market now.


You could use a cheap bms to lockout the existing forklift drive electrics, rather than paying for a large one to provide redundancy.

How often to forklift controllers fail and drain the battery to zero?

 

[crickets]

The active bms i am speaking of is just a series of buck converters that equalize the cell voltage, without wasting the difference in energy, in resistors. They dont care what the battery voltage is, only the difference in one cell to another. There are several on the market now.

I am familiar with those boards. They balance the cells (active balancers), but do nothing else a proper BMS does - undervoltage, overvoltage, overcurrent and overtemp/undertemp protections. If anything, they can be used in parallel with a BMS, since many BMSes have a pretty small balancing current and may be unable to balance out larger battery packs.

You could use a cheap bms to lockout the existing forklift drive electrics, rather than paying for a large one to provide redundancy.

How often to forklift controllers fail and drain the battery to zero?

Many forklifts (especially older ones) don't have undervoltage protection. In fact many of them are designed for 36/48v operation - they'd be happy to drain that Lithium battery to the point of total damage.

 

[604Pook]

you need the weight of the big battery...and probably pay way more for the EV battery

 

[crickets]

you need the weight of the big battery...and probably pay way more for the EV battery

Salvaged Leaf modules can go for anywhere between $60 and $90 depending on the age / SoH. That means the minimum configuration would run about $840 for batteries, let's say $300 for BMS, $100 for a pair of contactors and $15 for a fuse - so under $1300 and with a life expectancy of at least 5 years. Then those modules can be replaced while reusing the other components.

 

[gustafson]

I agree you need the weight. HOwever when they use special lead acids instead of standard form factor they get wicked expensive, and lithiums are so small it might make sense to partially replace the lead acids and leave them in for ballast. or create ballast

 

[steve-l]

I am not a fan of Lithium batteries over lead acid in many applications. Lithium chemistries offer lighter weight, but require special BMSs and are very temperature sensitive. So, for stationary applications and applications like a forklift where weight is a non-concern and where cold temperature performance is important, lead acid batteries are much better. Consider how long a forklift battery lasts. It is very likely your forklift battery is the original battery. Then consider the stated life of a Lithium battery is only 5 years. Now, compare costs. There is simply no comparison. Lead acid batteries are much cheaper, last longer and work much better in a wider temperature range.

 

[john.k]

And your old L/A battery can be sold for something like 20c/kg,or more ,to put towards a new one .

 

[gustafson]

I am not a fan of Lithium batteries over lead acid in many applications. Lithium chemistries offer lighter weight, but require special BMSs and are very temperature sensitive. So, for stationary applications and applications like a forklift where weight is a non-concern and where cold temperature performance is important, lead acid batteries are much better. Consider how long a forklift battery lasts. It is very likely your forklift battery is the original battery. Then consider the stated life of a Lithium battery is only 5 years. Now, compare costs. There is simply no comparison. Lead acid batteries are much cheaper, last longer and work much better in a wider temperature range.

Lead acid is also temperature sensitive. Who says lithium batteries only last 5 years? That would be news to all the people driving 10 year old EVs and Hybrids. Lead acids most applications [Like my Electrak] are significantly on their way out at 5 years. Ever leave a lead acid on a dumb charger and blow it up? Yup lead acid needs battery management too.
Really none of this is true, except that in a forklift the [lack of]weight is a negative consideration

 

[crickets]

I am not a fan of Lithium batteries over lead acid in many applications. Lithium chemistries offer lighter weight, but require special BMSs and are very temperature sensitive. So, for stationary applications and applications like a forklift where weight is a non-concern and where cold temperature performance is important, lead acid batteries are much better. Consider how long a forklift battery lasts. It is very likely your forklift battery is the original battery. Then consider the stated life of a Lithium battery is only 5 years. Now, compare costs. There is simply no comparison. Lead acid batteries are much cheaper, last longer and work much better in a wider temperature range.

How long the FLA battery lasts depends on the usage pattern of the forklift. If used 8 hours per day every business day, safe to say it would only last 2-3 years. In a setup with occasional use one may be able to push it to 5-6 years. Battery longevity is a product of cycling, age and maintenance. I have seen a few forklift batteries that were killed simply by operators forgetting to plug them in to charge after running them dry.

For Lithium 5 years I have pulled out of a hat. I was describing the costs associated with building custom batteries out of cheap salvaged EV cells which have already seen some significant use, but still having substantial utility afterwards. It's hard to say what the actual longevity would be, but the replacement cost is quite low which is what I was demonstrating. If you were to buy a new factory battery such as one of those Triathlons, it will last 20-25 years and provide for much smaller charging downtime for a heavily used lift truck.

 

[crickets]

And your old L/A battery can be sold for something like 20c/kg,or more ,to put towards a new one .

Current prices on the US West Coast are 8-10c per lb.

 

[gbent]

Check with your insurance carrier about lithium ion batteries in your shop. Some carriers are getting nervous about the lion fires. New York City has had a significant increase in fires caused by lion fires. Many of these fires are caused by what are being called "micromobility" equipment, such as e bikes and scooters. Many of these cheap machines fail quickly, and are often repaired by folks using generic parts. I expect this to become a more significant issue going forward as more vehicles move from virtue signaling garage queens to mainstream and have usage in much more adverse conditions than many current machines.

 

[goldenfab]

Lithium ion batteries used in EVs can really dangerous as others have said so make sure you use the right BMS and take the right precautions. There is another type of lithium battery tech called LiFePO4. Its a lot less dangerous and I think they are less expensive too. The drawback with them is if you charge them when they are too cold you ruin them. A lot of people use these batteries for off grid solar power, so you can find a lot of info on them for that use.

 

[crickets]

Lithium ion batteries used in EVs can really dangerous as others have said so make sure you use the right BMS and take the right precautions. There is another type of lithium battery tech called LiFePO4. Its a lot less dangerous and I think they are less expensive too. The drawback with them is if you charge them when they are too cold you ruin them. A lot of people use these batteries for off grid solar power, so you can find a lot of info on them for that use.

That is one of the functions of the BMS - to disable charging when battery temperature is below freezing (usually ~5C is the lower cutoff). A forklift battery can be made with LFP cells, but it would have to be larger as those cells aren't as happy with higher current draw unlike NMC cells found in EVs. It is also harder to find cheap large LFP cells, so the build cost goes up significantly. But indeed, they're otherwise inherently safer than NMC or NCA cells.

 

[memphisjed]

Lithium battery tech is here- I wonder why more new lifts do not use it. With proper cooling and heating they last a long time. My volt batteries still have great charge- they have active cooling and heating for running and charging. 5 years is a myth. Chevy warranties batteries for 10 years.