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Post by Deleted on Jan 14, 2020 20:10:30 GMT
Returning to the topic of batteries I have often wondered about using the Nickel Metal Hydride batteries out of Toyota Prius for boat purposes.
The packs are made up of 7.2v NiMH cells apparently.
Bit awkward to safely disassemble but it's quite interesting.
They change the whole unit if there are any failed cells so there might be quite a few good ones still.
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Post by peterboat on Jan 14, 2020 21:11:14 GMT
My valences can, hence I have a vaporised 13 mm deep socket wiped it out totally nothing left of one end of it Yes but they don’t have a “proper” BMS with a built in means to protect the battery from over or under charge by isolating it. Yours are a bit of a halfway house. It is the means to isolate the battery that presents the discharge current limitation. They have all that matters to me, the ability to balance the cells in charge and discharge plus measure temps in the battery and count the cycles. If I could get a master BMS programmed I could do the rest but the problem is valence and now lithiumworks are a closed shop for that sort of stuff!! However two years of use and no problems 13,2 on the gauge so all is well, no need to count amps or anything else
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Post by peterboat on Jan 14, 2020 21:14:36 GMT
Returning to the topic of batteries I have often wondered about using the Nickel Metal Hydride batteries out of Toyota Prius for boat purposes. The packs are made up of 7.2v NiMH cells apparently. Bit awkward to safely disassemble but it's quite interesting. They change the whole unit if there are any failed cells so there might be quite a few good ones still. I have the same in both my Hondas the cells normally get recycled into rebuilt packs, I have a supplier for my Honda insight but as yet it has been good, if it fails I will put a lithium pack into it for more power and better range
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Post by peterboat on Jan 14, 2020 21:22:32 GMT
Don't worry, I'm sticking at £70 per year for now until Tesla gets justice ;-) Now...who killed Tesla? Tesla shares are absolutely flying at the moment. Do you have inside information about a major correction? Stock price has tripled in 7 months. dont think Tesla will fold or fail they are without a shadow of a doubt the best electric vehicle maker in the world, they seem to have the market sewed up and are making the cars that the market wants. I think they will get cheaper as time goes on and economies of scale really kick in, other car makers are struggling to produce anything half as good. which for them is a disaster. Whats going to happen when they start making electric super minis for towns and extended range I suspect we will hear lots of loud screaming from major car makers
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Post by Deleted on Jan 14, 2020 21:25:25 GMT
I wonder if other auto companies will end up using their production capacity to manufacture Tesla vehicles under license.
It's definitely interesting.
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Post by Telemachus on Jan 14, 2020 22:46:11 GMT
Yes but they don’t have a “proper” BMS with a built in means to protect the battery from over or under charge by isolating it. Yours are a bit of a halfway house. It is the means to isolate the battery that presents the discharge current limitation. They have all that matters to me, the ability to balance the cells in charge and discharge plus measure temps in the battery and count the cycles. If I could get a master BMS programmed I could do the rest but the problem is valence and now lithiumworks are a closed shop for that sort of stuff!! However two years of use and no problems 13,2 on the gauge so all is well, no need to count amps or anything else Yes but you don't charge with an alternator, and you are careful not to over-discharge. If one wants a fairly foolproof system then I suggest that having an automatic emergency disconnect for low or high voltage is very sensible, otherwise you risk destroying the very expensive batteries in a brief period of carelessness.
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Post by Telemachus on Jan 14, 2020 22:54:14 GMT
Returning to the topic of batteries I have often wondered about using the Nickel Metal Hydride batteries out of Toyota Prius for boat purposes. The packs are made up of 7.2v NiMH cells apparently. Bit awkward to safely disassemble but it's quite interesting. They change the whole unit if there are any failed cells so there might be quite a few good ones still. NiMH are quite good - the primary battery in my glider is NiMH. I just did a capacity check having owned the glider for 5 years and not knowing the history of these batteries before I bought it - capacity still at 9AH as the maker intended.
The thing with NiMH is that, a bit like Lithium, you need to charge them correctly. I don't mean you charge them the same as Lithium, I mean you can't really charge them with a standard lead acid charger or alternator. They hoover up the current quite nicely but as they approach fully charged, instead of the supplied electrical energy going to adding charge, it goes to generating heat. Not damaging within reason, however as the temperature rises the battery voltage falls and thus more current is taken from the charger / alternator. And thus it gets hotter and the terminal voltage drops further. Otherwise known as thermal runaway. Eventually it boils and explodes, spraying corrosive sodium hydroxide everywhere. Nasty!
A NiMH charger has to detect when the batteries start to heat up, which it does by detecting the reduction in terminal voltage, and then shut itself off to avoid thermal runaway.
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Post by Deleted on Jan 14, 2020 22:58:28 GMT
How about a single lead acid battery off engine alternator and an inverter running a NiMH charger to a NiMH battery bank in the cabin.
A bit inefficient but it could work. Possibly. While engine is running.
Assuming engine running means boat going along. Obviously a main engine is not a valid prime mover for domestic electricity in general.
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Post by Telemachus on Jan 14, 2020 23:03:08 GMT
How about a single lead acid battery off engine alternator and an inverter running a NiMH charger to a NiMH battery bank in the cabin. A bit inefficient but it could work. Possibly. While engine is running. Assuming engine running means boat going along. Obviously a main engine is not a valid prime mover for domestic electricity in general. Yes that would work but as you say, a bit inefficient. You would have to remember to turn off the inverter / charger when you stopped the engine!
I haven't looked, but can't recall coming across a NiMH charger designed to charge a large battery. They must surely exist, but at what price?
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Post by Clinton Cool on Jan 14, 2020 23:04:39 GMT
I have a single 105AH 12v Trojan. With a daily usage of 20AH or so, it's all I need. I've had the battery for just over 3 years. During this time the battery has been fully charged every day for 8 months of the year (375w solar). For 2 of the other 4 months I charge daily with a generator until around 2 amps are going in. The odd sunny winters day and a bit of cruising will see the tail current when running the genny at around 1.2a. I leave the boat with solar connected for the other 2 months so the battery is fully charged during this time. My battery has never been below 12.2v rested. When genny charging I do it through a modern Sterling battery charger set at 14.8v with float voltage the same. I've noticed over this winter that the voltage in the morning would tend to be 12.3 or 12.4 whereas in previous winters 12.5 was the norm. It seems I may have lost a fair bit of capacity.
I'm a long way from the charger's manual at the moment but seem to recall that the maximum voltage I can set on the charger is 15v so a desulphation charge isn't possible.
What's the consensus, should I try the trick of taking the battery down to 20%? I could do this by turning off solar when I get home, the switching it back on one morning when the battery is low. Or should I buy a bench power supply where I can set a higher voltage, just for occasional desulphation?
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Post by Deleted on Jan 14, 2020 23:10:03 GMT
How about a single lead acid battery off engine alternator and an inverter running a NiMH charger to a NiMH battery bank in the cabin. A bit inefficient but it could work. Possibly. While engine is running. Assuming engine running means boat going along. Obviously a main engine is not a valid prime mover for domestic electricity in general. Yes that would work but as you say, a bit inefficient. You would have to remember to turn off the inverter / charger when you stopped the engine!
I haven't looked, but can't recall coming across a NiMH charger designed to charge a large battery. They must surely exist, but at what price?
I was thinking the NiMH could be sized to exactly match the expected daily power consumption. Might actually be quite a small battery. I suppose lithium stuff has superceded it to be fair.
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Post by Deleted on Jan 14, 2020 23:16:33 GMT
I have a single 105AH 12v Trojan. With a daily usage of 20AH or so, it's all I need. I've had the battery for just over 3 years. During this time the battery has been fully charged every day for 8 months of the year (375w solar). For 2 of the other 4 months I charge daily with a generator until around 2 amps are going in. The odd sunny winters day and a bit of cruising will see the tail current when running the genny at around 1.2a. I leave the boat with solar connected for the other 2 months so the battery is fully charged during this time. My battery has never been below 12.2v rested. When genny charging I do it through a modern Sterling battery charger set at 14.8v with float voltage the same. I've noticed over this winter that the voltage in the morning would tend to be 12.3 or 12.4 whereas in previous winters 12.5 was the norm. It seems I may have lost a fair bit of capacity. I'm a long way from the charger's manual at the moment but seem to recall that the maximum voltage I can set on the charger is 15v so a desulphation charge isn't possible. What's the consensus, should I try the trick of taking the battery down to 20%? I could do this by turning off solar when I get home, the switching it back on one morning when the battery is low. Or should I buy a bench power supply where I can set a higher voltage, just for occasional desulphation? It sounds like a pretty sorted system to me. In the old days of black and white tellies I remember waiting for the picture to start getting smaller that means batteries want charging. No longer have a telly so have to rely on instinct.
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Post by peterboat on Jan 15, 2020 0:20:49 GMT
Returning to the topic of batteries I have often wondered about using the Nickel Metal Hydride batteries out of Toyota Prius for boat purposes. The packs are made up of 7.2v NiMH cells apparently. Bit awkward to safely disassemble but it's quite interesting. They change the whole unit if there are any failed cells so there might be quite a few good ones still. NiMH are quite good - the primary battery in my glider is NiMH. I just did a capacity check having owned the glider for 5 years and not knowing the history of these batteries before I bought it - capacity still at 9AH as the maker intended.
The thing with NiMH is that, a bit like Lithium, you need to charge them correctly. I don't mean you charge them the same as Lithium, I mean you can't really charge them with a standard lead acid charger or alternator. They hoover up the current quite nicely but as they approach fully charged, instead of the supplied electrical energy going to adding charge, it goes to generating heat. Not damaging within reason, however as the temperature rises the battery voltage falls and thus more current is taken from the charger / alternator. And thus it gets hotter and the terminal voltage drops further. Otherwise known as thermal runaway. Eventually it boils and explodes, spraying corrosive sodium hydroxide everywhere. Nasty!
A NiMH charger has to detect when the batteries start to heat up, which it does by detecting the reduction in terminal voltage, and then shut itself off to avoid thermal runaway.
I have a grid charger in the Insight it turns on the fan to cool the batteries down, I charge for 36-48 hours every 3 months to keep the battery pack balanced. I did forget about it once and it was on for 4 days no harm done the maker of the charger is most likely the senior insight expert going clever guy.
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Post by JohnV on Jan 15, 2020 7:54:22 GMT
They have all that matters to me, the ability to balance the cells in charge and discharge plus measure temps in the battery and count the cycles. If I could get a master BMS programmed I could do the rest but the problem is valence and now lithiumworks are a closed shop for that sort of stuff!! However two years of use and no problems 13,2 on the gauge so all is well, no need to count amps or anything else Yes but you don't charge with an alternator, and you are careful not to over-discharge. If one wants a fairly foolproof system then I suggest that having an automatic emergency disconnect for low or high voltage is very sensible, otherwise you risk destroying the very expensive batteries in a brief period of carelessness. have you noticed these devices ? www.force4.co.uk/sterling-battery-to-battery-chargers.html?utm_source=google_shopping&195=10368&gclid=CjwKCAiA6vXwBRBKEiwAYE7iS3A5pz3NSTZN6-91Sem0eC1L-fSvxERXmSmhTXLGQ4W8sge1rwgKOhoC0RQQAvD_BwEthey have a LiFePO4 setting so just run it off the starter battery. incidentally the same argument for low voltage disconnect applies to Pb as well
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Post by Telemachus on Jan 15, 2020 10:08:23 GMT
Sterling do the AtoB (alternator to battery) as well as the B2B you mention above. The B2B would I think do the job, though I'm not a fan of Sterling stuff. But at quite a price if you want one that can pump a reasonable amount of current out. The A to Bs are cheaper but, while I can't be sure, I suspect that they only boost the voltage, they cant reduce it. So you would need a basic alternator regulator voltage down at say 13.6 and use the A2B to increase it. I am fairly sure an AtoB can't say reduce 14.4v output to 13.6v. All of which is of course why I am designing my own alternator controller - long term project though.
No I disagree that the same low disconnect argument applies to LA. LA batteries make it obvious they are getting flat - light go dim over a prolonged period. Whereas LiFePO4 hold up and are fine - right until the moment the voltage crashes. And anyway, fully discharging a LA battery, whilst bad for it, isnt catastrophic. Fully discharging a LiFePO4 battery is catastrophic. As borne out by the fact that drop in LiFePO4 replacements have low voltage cut off whereas I don't think any or many LA installations have it.
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