I have a battery out of a electric car. The battery contains 28 individual cells that are rated at 7.2v. I want to charge this with solar. Tieing 6 cells in series to produce around 48vdc. I need a way to use some sort of
Battery Charger Protection Board to protect each cell. Any body have any ideas?
7.2v is commonly called “2S” in the LiPo battery world, check out some projects online/youtube builds where someone installs a 48v solar system using 2S batteries and set yourself up similarly…you’ll need an MPPT for sure, we sell this one https://www.sparkfun.com/products/12885 that can help 
I think @ern is truly referring to a NiMH battery pack and not a LiPO one. NiMH would indeed be 7.2V whereas LiPO 2S would be 7.4. Interestingly when I was looking for NiMH solar charger, I could not find dedicated ICs (for solar) like they seem to be for LiPO technology; probably the market is heavily skewed towards LiPOs because of their incredible energy density and perhaps also their market absorption. But there are certainly non-solar ICs and circuits for charging NiMH technology that can be adapted to solar (DS2715 is such an IC - eBay seems to have more than a few iterations of such circuits).
A few other ICs: MAX712, BQ2002, LTC4060 (the first two seem to be the ubiquitous choices).
Yes nimh is what i am looking for and to separate the cells to produce 48v. I did look at some videos that talk about these batteries but I have found none that talk about using these with solar.
Somebody out there is doing this
Thanks for your help
Depends on what you mean by “protect”.
Some series battery chargers use a charge balancer circuit to prevent the voltage of individual cells from exceeding the design voltage, if one or more cells fails to charge. For NiMH batteries, all you need is two diodes in series, in parallel with each cell, as shown here: https://www.electroschematics.com/balan … ery-packs/
Other circuits are possible depending on your goal. Try the search phrase “series battery charge balancer schematic”.
NiMH cells are nominally 1.2V, so by "individual cell" do you mean an assembly of 6x1.2V NiMH?28 individual cells that are rated at 7.2v
In any case, people disassemble such packs, measure the capacity of each individual cell, and discard the weak ones. Find tutorials about that by search for “salvaging laptop battery packs”.
This is one of 28 cells that Make up a battery pack that goes in a prius hybrid car. They have to be pressed from side to side else they swell when charged i guess the case is thin.
I don’t think their is multiple cells inside the case. Haven’t taken one apart.
So, basically, you do not know what you have in that photo.
The chemistry of NiMH batteries leads to the 1.2V (nominal) per cell. It doesn’t matter what the shape or size of that cell might be.
I am not 100% you are right about that. I will check some things and will let you know.
It is a very good idea to do the basic research!
A quick web search shows that they are a series string of 6 1.2V 5Ah prismatic NiMH cells. So yes, time for some basic reserarch. At least as NiMH, they are less likely to spontaneously combust.
Ues you are right. This is a module, made up of 6 1.2v cells = 7.2v. Now I want to tie these 7 of these in series to produce 48v os close. I want to regulate each module to charge them separately. Can any body out there help me with that?
You will need custom circuitry for that, for the “48V” (more likely, 58-60V) charger and for the seven charge balancers.
You can find some examples for lithium based battery packs, which could serve as guidelines, but it seems likely that the Youtubers who demonstrate the dismantling of Prius batteries would have some leads.
Wow was hoping somebody out there would have a better idea. I can do a lot of things but am limited in electronics. Can do if i have instructions to go by. If I could get an idea but I can stumble around YouTube and get nowhere.
If somebody out there has an idea let me know.
Thanks
What could possibly be a “better idea” than a custom charger/balancer design, for your very unusual requirement? Were you hoping to buy something off the shelf?
Hire someone to do the design and construction work – it is neither challenging nor interesting. The Arduino forum has a Jobs and Paid Collaboration section that seems to work.
The right panel (Discrete Balancing) is an example of the TYPE of balancer circuit that would work, if parameters were appropriately altered for the charge current and 8.4V cutoff of a fully charged 6S NiMH pack (from https://sound-au.com/articles/lithium-charging.htm)
https://sound-au.com/articles/lipo-f4.gifThanks for your advice. I probably do need some help from somebody that knows a little more than I. The website u sent me to goes on and on and I can’t follow. (Don’t have enough knowledge on this subject).
Thanks for your help.
Can’t charge nimh batteries like li-ion batteries so the picture and website you show aren’t really help because they are totally different batteries. Nimh are more similar to the old ni-cad batteries.
Copied from a website
NiMH batteries are a much more modern phenomenon. Research and development began at the Battelle-Geneva Research Center in 1967, and was satisfactorily completed in 1987.
The chemical composition of a standard nickel-metal hydride battery looks like this: a nickel hydroxide positive electrode plate, a hydrogen ion negative electrode plate, a separator, and an alkaline electrolyte such as potassium hydroxide.
It is much easier and safer to charge NiMH batteries than the more recently developed and rather dangerous lithium based batteries. NiMH batteries are also much more tolerant of abuse than lithium based batteries.
With NiMH batteries you can employ constant current charging (up to a voltage limit), trickle charging, or float charging. Charge balancers are still necessary for NiMH battery packs, as attested by the design of the Prius battery packs.
You need to either do quite a bit more research, or, as suggested earlier, hire an professional to design the charger/balancer.
You got any ideas on where i can get such a person to design or give me a parts list and a diagram of where to put the parts? Or build it.
I already mentioned the Arduino Jobs and Paid Collaboration forum section.
ern:
You got any ideas on where i can get such a person to design or give me a parts list and a diagram of where to put the parts? Or build it.
I’ve only bought batteries from them but these guys seem to know a bit about chargers, too:
