New Battery Etc

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Re: New Battery Etc

Postby Burgerman » 29 Mar 2019, 14:03

Charging batteries is easy. You just use the shitty mobility charger that it came with, plug in till you get a green.

That works. ANYTHING works. But its all a matter of how well.

Apart from incomplete charging, causing sulfation build up, most mobility chargers and automatic one size fits all chargers charge at a too high 28.8 to 29.4V.

The CORRECT voltage to charge a gel battery would be a MAX of 28.2V (14.1V each). And a MIN 27.6V (13.8V). Or less. Thats at 20 centigrade. The battery may actually be warmer than your room. And the room may be 30 centigrade in summer...

The perfect voltage or best cycle life would be 13.95V or 27.9V charge at 20C. Or a MAX limit of 28.2V.
Not the typical 28.8 to 29.4V we see on generic gel/AGM batteries.

The difference seems small but...
Now take a look at this... Would you prefer 500 cycles or 300?
Image1.gif
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Re: New Battery Etc

Postby granian » 29 Mar 2019, 15:00

The correct voltage for my Odyssey battery being 14.5 to 14.7 , is there a chart like the one you just posted for Odyssey batteries or is it similar.
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Re: New Battery Etc

Postby Burgerman » 29 Mar 2019, 16:41

Similar, but less pronounced.
Too high voltage on a sealed recombinant battery causes the following. If you increase voltage beyond the temp/maxCV point the battery gasses faster than the recombination can work. (all lead batteries gas as they start to become full, and do so more as the voltage is raised). Recombination means the hydrogen and oxygen gets turned back into water. That happens up to about the 14.7V level fast enough that the battery which is sealed does not build pressure and vent, so it doesent lose electrolyte. The recombination causes heat... The heat means that you must lower the voltage. Or the current starts to rise and makes more gas, more heat... So 14.7 at 20C is the safe point on a healthy battery.

The reason you cant do that 14.7V on a gel which is also a recombinant battery but LESS SO, is because it produces bubbles and voids in the thick paste gel. Which dont recover... And so the gel dries out, shrinks and the battery goes higher resistance. Its unwise!

The reson that you can do 14.7V on a optima or odyssey battery rather than the 14.4 or 14.5 on a typical AGM battery is because the lead grid is pure. And the lead paste filling the grids is also 99.99+ pure virgin lead.Theres only 1 metal in there. Other cheap AGM batteries use reclaimed lead, with impurities in it. Different metals. And they also need to add antimony, calcium, tin and selenium, and other metals to give the reclaimed cheaper lead strength. Pure lead doesent need these additives. Plates can be made thinner. And so there are no mixed metals and impurities sat in acid causing unwanted corrosive gassing and plate corrosion. But in a typical cheap AGM using 14.7V causes too much gassing and they corrode faster while being charged. They also have naturally higher impedance. Why? Because with all those impurities and different metals, they need to use a weaker acid electrolyte to get decent cycle life... So they have less cranking amps, higher impedance. Thats why the odyssey can start a truck, AND be deep cycled.
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Re: New Battery Etc

Postby granian » 29 Mar 2019, 17:49

I had read a little about the Odyssey batteries regarding the pure lead thinner plates. I did not realise that the lesser batteries so to say, were made from recycled materials. A good explanation and I can see how passionate you are about batteries, much learnt over the years. :thumbup:
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Re: New Battery Etc

Postby Burgerman » 29 Mar 2019, 18:08

I used to sell batteries. I still get mail shots from chinese companies that will sell me pretty looking grp24 deep cycle batteries with whatever I want on the label. So if you want a new 'brand' and spec, it can be printed and stuck on the batteries all for your own company. As long as I buy a pallet or two, they are around 20 uk pounds each. 80Ah, deep cycle, etc. The world is flooded with them. Thousands of different ones. All the real battery manufacturers are having to compete with this garbage. And going out of business trying, as people dont know the difference. For all intents, the real difference is impedance, which is everything. Because to get even 350 cycles out of them they must use very weak electrolyte compared to a pure virgin lead battery. A 75Ah Optima battery, used to cost me 170 years back. So theres a big difference in there somewhere. Odyssey are even better for Ah per volume and for us.

Go price up the cost of virgin uncontaminated 99.99 percent pure lead. And be horrified. Its many times more expensive.

Impedance...
The 68Ah Odyssey, has 2.5mOhm impedance. Can do a 1,500A startng current for 5 secs which is a long time. And has a CA figure of about 950A from memory.
Can be charged and should be charged at the highest Amp level you can provide. They recommend their 50A charger even for the smallest 12Ah odyssey. It can be charged from 100% discharged to 95% full in 60 mins. Claimed 450 x 80% discharge cycles. But FULLY charged after use, you can exceed that. Which is easy on the odyssey as it charges more completely overnight. The gel needs about 12 hours or longer.

The 74Ah MK gel is double the impedance at 4.5mOhm. Making them HALF as good under load. Peukert, which shrinks the battery, is heavily related to impedance and so the gel has more... It has a max current of 405Amps. It has no CA figure because its not advised and you would need 3 to equal the smaller odyssey. Can only be charged at 24A. Claimed 500 x 80 percent discharge cycles. But only if charged CORRECTLY which they normally are not.

The common also ran chinese AGMs are useless. SOME expensive AGMs are OK ish, such as the ones now fitted to the sunrise chairs. But not many match the Odyssey.
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