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Old 13-03-2012, 08:38   #1
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Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Hello all,
I'm a technician for a startup battery company. In my search for new markets I remembered my grandparents lamenting the "stinkpots" on the lakes and lagoons during their sailing trips, and wishing they didn't need to use small gas outboards to navigate congested marinas, etc. It seemed to me that electric motors, which could be either plugged in or charged via wind or solar means, would be preferable. After looking into it, I've noticed a prevailing dissatisfaction with most lead-acid systems used to power on-board electronics and motors. The charging inefficiencies (including the length of time it takes to charge), short lifespan, and maintanance requirements seem to be a fairly big hassle that could take something away from a day (or several) out on the water.
We have bipolar NiMH batteries that can charge (from a fully discharged state to a fully charged state) in an hour without significantly effecting cycle life. The charge acceptance is much more efficient than lead-acid therefore needing less overall energy generation (from solar or wind) to charge. Also for charging with wind turbines, there is practically no need to limit the charge current (for a 50 Ah battery-50 amps, for a 100 Ah battery-100 amps).
I am looking for feedback from potential consumers and from potential partners regarding the replacement of lead-acid batteries with bipolar NiMH batteries. Thanks for your input!
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Old 13-03-2012, 09:04   #2
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

From my experience with laptop batteries, NiMH would be the last thing I would use on my boat.
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Old 13-03-2012, 10:17   #3
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Don,
It may be that you are refering to the Lithium-Ion batteries used in most laptop computers. Lithium-based chemistries do tend to have fiery catastrophic failures. Our product is a Nickel-Metal Hydride chemistry which (if it fails) is generally very safe. And of course, we have further safety features built into the architecture. NiMH chemistries have been around for quite a long time (it is what is used in the Prius hybrid) and as far as I know, there have never been injuries linked to these batteries themselves.
As far as today’s NiMH latop batteries are concerned, I cannot personally speak to their performance, and I would be interested to know what problems you may have experienced with them. However, I can tell you that cell and battery architecture plays a huge role in the performance and reliability of this chemistry.
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Old 13-03-2012, 10:19   #4
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Three areas come to mind:

1) Failure modes. Can you compare NiMH to lead-acid, please? Off-gassing, sulfation, drying out, spilling, etc. for lead-acid. How do NiMH batteries compare?

2) Price. Including expected life-span, of course.

3) Compatibility with existing equipment-- for example, inverter/chargers. Do I have to replace all of that, too? Plain, old alternator on the engine ok? etc., etc.

Kirk
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Old 13-03-2012, 10:38   #5
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

There is at least one vendor that has a deep cycle non lead acid battery- Mastervolt. I think it is a Li-poly, but not sure.

The price is about triple that of an AGM and 5 times a lead acid. Seems like it has about 2-3 times the energy density of a lead acid.

David
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Old 13-03-2012, 10:53   #6
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Quote:
Originally Posted by BatteryPower View Post
Don,
It may be that you are refering to the Lithium-Ion batteries used in most laptop computers. Lithium-based chemistries do tend to have fiery catastrophic failures. Our product is a Nickel-Metal Hydride chemistry which (if it fails) is generally very safe. And of course, we have further safety features built into the architecture. NiMH chemistries have been around for quite a long time (it is what is used in the Prius hybrid) and as far as I know, there have never been injuries linked to these batteries themselves.
As far as today’s NiMH latop batteries are concerned, I cannot personally speak to their performance, and I would be interested to know what problems you may have experienced with them. However, I can tell you that cell and battery architecture plays a huge role in the performance and reliability of this chemistry.
Yes, I could be confused on the battery chemistry. I wasn't as concerned about my laptops catching fire as the fact that the battery life was less than 2 years for some really expensive replacements.

My Prius is only 2 months old, so I'm reserving judgement on its batteries. However, the battery management system on the car seems to keep the minimum charge at about 80% of capacity.

The biggest problem with the lead-acid batteries on a sailboat is that they tend to die quickly if you don't keep near a full charge on them. If you can tell me that your batteries can sit around for years at less than 50% charge without damage, maybe I'm interested. The typical sailboat use would be to pull 100 amp-hrs out of a 12v bank each day, running between 50 and 80% state of charge. For that we need a 400 amp-hr lead acid bank and we get 5 to 7 years battery life (daily use) at a replacement cost of $1000 (double that if you get stuck buying in exotic places). What do the numbers look like for NimH?
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Old 13-03-2012, 11:16   #7
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Welcome to Cruiser Forum, interesting stuff. Michael..
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Old 13-03-2012, 11:24   #8
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

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Originally Posted by donradcliffe View Post
...My Prius is only 2 months old, so I'm reserving judgement on its batteries. However, the battery management system on the car seems to keep the minimum charge at about 80% of capacity...
<aside>
My Prius is a 2005 and still going strong with original batteries. Would buy another in a heartbeat.
</aside>
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Old 13-03-2012, 11:30   #9
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

NiCd : the "first" mass-used fast rechargeable battery, memory effect, cycles approx 1000
NiMh : successor of NiMh, fast rechargeable, no memory effect, cycles approx 1000

Cost is between Pb and Li batteries ... approx $1.50 per 1000mAh.

NiCd and NiMh are mostly used as cylindrical cells at 1.3V and capacity of 100mAh <-> 4000mAh.

Would be interesting to know how these "marine" approved NiMH batteries are built like (thousands of cells ?).

BTW : if these cells are fast charged (1h instead of regular 12h) then they get VERY hot !
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Old 13-03-2012, 13:22   #10
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

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Originally Posted by Zonker View Post
NiCd : the "first" mass-used fast rechargeable battery, memory effect, cycles approx 1000
NiMh : successor of NiMh, fast rechargeable, no memory effect, cycles approx 1000

Cost is between Pb and Li batteries ... approx $1.50 per 1000mAh.

NiCd and NiMh are mostly used as cylindrical cells at 1.3V and capacity of 100mAh <-> 4000mAh.

Would be interesting to know how these "marine" approved NiMH batteries are built like (thousands of cells ?).

BTW : if these cells are fast charged (1h instead of regular 12h) then they get VERY hot !
Zonker, Our unique architecture is vastly different from standard wound NiMH batteries and there is very heat generation during a standard 1 hour charge. In fact, for simulated lifecycle testing we run continuous 1 hour charge and discharge cycles at elevated temperatures between 40-80 degrees C (104-176 F). After 50 cycles, we run a much more vigorous test (including 5C rate charge and discharges - 100 amps for our 20 Ah cells) before placing them back on another 50 cycle loop. Our current designs go out about 8 of these test loops. And each cycle is full depth of discharge for the rated capacity.
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Old 13-03-2012, 13:32   #11
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Quote:
Originally Posted by donradcliffe View Post
Yes, I could be confused on the battery chemistry. I wasn't as concerned about my laptops catching fire as the fact that the battery life was less than 2 years for some really expensive replacements.

My Prius is only 2 months old, so I'm reserving judgement on its batteries. However, the battery management system on the car seems to keep the minimum charge at about 80% of capacity.

The biggest problem with the lead-acid batteries on a sailboat is that they tend to die quickly if you don't keep near a full charge on them. If you can tell me that your batteries can sit around for years at less than 50% charge without damage, maybe I'm interested. The typical sailboat use would be to pull 100 amp-hrs out of a 12v bank each day, running between 50 and 80% state of charge. For that we need a 400 amp-hr lead acid bank and we get 5 to 7 years battery life (daily use) at a replacement cost of $1000 (double that if you get stuck buying in exotic places). What do the numbers look like for NimH?
Don, thanks for your input. This is very useful information about the battery use in real life. The actual price is not yet available because as of now we are in the sample stages of this development, but for the high-powered designs we are targeting roughly $1.20/Wh. With the numbers you gave me for lead-acid you are paying about $0.83/Wh. This of course doesn’t take into account the charge-rate discrepancy. For example, if you run a 100Ah Pb-acid pack down in 12 hrs, you would have to recharge overnight. With a 100Ah NiMH pack, you could run it 12 hrs, recharge it in an hour, and go out again for another 12 hrs.
Right now I have a 5 cell battery that has been sitting near my desk for 6 months after being partially discharged (running some small motors), and it still has pretty close to the same voltage (about 1.15V/cell). Also, with these batteries the very slow self-discharge does not (unlike lead-acid) really affect the battery, so if you left your battery alone for a year you could just recharge it in an hour (maybe less depending on the state of charge) and get back on the water.
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Old 13-03-2012, 13:56   #12
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Quote:
Originally Posted by Kirok View Post
Three areas come to mind:

1) Failure modes. Can you compare NiMH to lead-acid, please? Off-gassing, sulfation, drying out, spilling, etc. for lead-acid. How do NiMH batteries compare?

2) Price. Including expected life-span, of course.

3) Compatibility with existing equipment-- for example, inverter/chargers. Do I have to replace all of that, too? Plain, old alternator on the engine ok? etc., etc.

Kirk
I spoke briefly with another tech and he said that your alternator would be fine to charge the battery but of course it would require a NiMH suited controller. The main difference in charging NiMH versus charging lead-acid is that lead acid is constant voltage and NiMH chargers are usually constant current. The tech I spoke to thinks we may be able to use lead-acid chargers with minor adjustments.
There shouldn’t be any outgassing, drying out, or spilling with these batteries.
I believe I addressed your other questions in previous posts.
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Old 13-03-2012, 14:01   #13
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Quote:
Originally Posted by BatteryPower View Post
Zonker, Our unique architecture is vastly different from standard wound NiMH batteries and there is very little heat generation during a standard 1 hour charge. In fact, for simulated lifecycle testing we run continuous 1 hour charge and discharge cycles at elevated temperatures between 40-80 degrees C (104-176 F). After 50 cycles, we run a much more vigorous test (including 5C rate charge and discharges - 100 amps for our 20 Ah cells) before placing them back on another 50 cycle loop. Our current designs go out about 8 of these test loops. And each cycle is full depth of discharge for the rated capacity.
Gaaahh Sorry! VERY LITTLE HEAT GENERATION!
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Old 13-03-2012, 14:08   #14
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Hi ... When will you have a price list and availability ... 500 amp hr pack and expected number of charges using 80% plus size and weight, Charge voltage and charge current. How do they compare to lifPo4
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Old 13-03-2012, 14:13   #15
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Re: Startup looking to replace Lead-acid with Nickel-Metal Hydride (NiMH)

Me too...Michael..
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