Making a Charger for NI/FE Batteries

[Cow Bay Bob]

I have a small problem I have got a 24 volt 500 amp hr bank of NI/FE {Edison } Batteries Bought them 7 years ago. Was told when I bought them to Work them really hard they love it. Also was told they don't wear out. But I would eventually have to drain them out and rejuvinate them. I have done this to 5 cells 2 of them worked perfectly 3 of them not so. Been told to cycle them in by Charging them right up then Flatten them. 3 or 4 times. This is where my problem is , I have been told to charge them at 100 amps , my solar is flat out at 35 amps, as I live in the rainforest I have only a short window of Sunshine because of tree shadow or rain. The cells are only 1.2 volt, i have a Woods Charger that will self adjust down that low but I cannot wind it up over 15 amps. So I either make a special Rack of solar panels too charge 100 amps, again hampered by short window of sunshine. Or build a special Battery Charger 1.5 volt x 100 amps. I have access to a 22 KVA Generator at my workshop to run it. What I need is a wiring Diagram and parts list to build such an animal . Or advice who to ask. Cheers Cow Bay Bob.

 

[NIFE]

I have a small problem I have got a 24 volt 500 amp hr bank of NI/FE {Edison } Batteries Bought them 7 years ago. Was told when I bought them to Work them really hard they love it. Also was told they don't wear out. But I would eventually have to drain them out and rejuvinate them. I have done this to 5 cells 2 of them worked perfectly 3 of them not so. Been told to cycle them in by Charging them right up then Flatten them. 3 or 4 times. This is where my problem is , I have been told to charge them at 100 amps , my solar is flat out at 35 amps, as I live in the rainforest I have only a short window of Sunshine because of tree shadow or rain. The cells are only 1.2 volt, i have a Woods Charger that will self adjust down that low but I cannot wind it up over 15 amps. So I either make a special Rack of solar panels too charge 100 amps, again hampered by short window of sunshine. Or build a special Battery Charger 1.5 volt x 100 amps. I have access to a 22 KVA Generator at my workshop to run it. What I need is a wiring Diagram and parts list to build such an animal . Or advice who to ask. Cheers Cow Bay Bob.

You can make a low voltage, high current power supply from a microwave transformer. You would also need a Variac and some industrial grade diodes. Do your batteries have metal or plastic cases?

 

[Cow Bay Bob]

Plastic Cases. Are you suggesting a microwave transformer from a home kitchen grade Micro Wave or something more serious.?

 

[NIFE]

Plastic Cases. Are you suggesting a microwave transformer from a home kitchen grade Micro Wave or something more serious.?

Larger kitchen grade, 1000 watt.

Are the cells "Iron Edison" brand.

 

[Cow Bay Bob]

No they are " Iron Core "

 

[NIFE]

No they are " Iron Core "

My experience is with the original Edison nickel iron cells. The charger I made is 75 Amp but you could make a 100 amp if you wind it a little differently. The most effective fixes for the weak cells I have are an electrolyte change and reverse charging. The Iron Core brand positive plate is constructed different from the original Edison's. The reverse charging method might permanently damage them. The major components for the charger are a microwave transformer, variac to adjust the microwave transformer primary coil, AWG2 wire, and Semikron brand diodes. Before going through all the effort, try a little Kepner Tregoe. I.E why did 2 of 5 work perfectly, what is the definition of perfect vs not so perfect. Source of electrolyte, age of the potassium hydroxide, were any cell plates exposed for an extended length of time etc.

 

[Cow Bay Bob]

Why 2 of 5 worked is a mystery. Contacted my supplier and he suggested the 100 amp recharge x 3 times to get them back on track. The two that worked are back in the system and not crashing out. the other three are down to .400/ .300 volts when the Invertor knocks off from Low Voltage. The Demineralised Water comes from a Comercial Chemical outlet. and the KOH is brand new. And I have kept the fluid level up to the cells. I am lucky enough to have a pretty clever Electrical Wizard { He frightens me at times} on hand , He has got the Idea in his head, and asked if I could find any more info, which is why I am on this site. Cheers Bob

 

[NIFE]

Why 2 of 5 worked is a mystery. Contacted my supplier and he suggested the 100 amp recharge x 3 times to get them back on track. The two that worked are back in the system and not crashing out. the other three are down to .400/ .300 volts when the Invertor knocks off from Low Voltage. The Demineralised Water comes from a Comercial Chemical outlet. and the KOH is brand new. And I have kept the fluid level up to the cells. I am lucky enough to have a pretty clever Electrical Wizard { He frightens me at times} on hand , He has got the Idea in his head, and asked if I could find any more info, which is why I am on this site. Cheers Bob

Nice to have an Electrical Wizard around. What is the highest voltage the weak cells get to during charging ? I built my charger for the same reason as you, none available. If you want to go ahead with the project, the first step would be to find an old microwave. Make sure it is not the inverter type. It would need to be one of the larger ones such as an over the range or a countertop rated at 900-1000 watts microwave power, not input power. Be careful when disassembling. There is a high voltage capacitor near the transformer that may still have power in it. Discharge it by shorting out the capacitor terminals with an insulated screwdriver. Another alternative is to use a DC welder for a charger. The problem with those is most are around 20% duty cycle. It would take a long time to charge under those conditions.

 

[Cow Bay Bob]

Thanks for your reply, Have limited access to old micro waves here especially bigger ones. They do turn up at the local dump ocasionally. Remember we are in an area of no grid power and Micro waves are a bit of a no no on most home solar power set ups. But I do have access to quite a few Old Woods 12/24 volt Battery chargers. Most of them Cooked from being turned up to high to try and charge large Solar Battery Banks or being run on too small Generator. Will see what me Wizard came up with. Cheers

 

[Cow Bay Bob]

This is as far as we have got at the momment. And it is working putting out 80+ amps @ 1.75 volts. The clear Battery is a box I had made up after we broke one in a shift its good cause we can see whats going on inside it. The Wizard gutted an old Woods Charger and rewound another coil to suit his needs . We shall see what happens