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Re: (ET) 8v battery in the mix?
I can easily charge the 6v batteries as two twelves and a 6. Hadn't
thought about how to charge the 8v though. :-)
<'good-enough for today' solution somehow remains in effect for a couple
of years>
Yeah, been there all too often! ;-)
Thanks for all the thoughts.
Thon
On May 26, 2017, at 2:40 PM, Darryl McMahon wrote:
> It probably won't hurt anything on the tractor. The voltage tolerances
> needed to accommodate everything from an over-charged 36-volt nominal
> pack to a discharged pack is a big enough range that another 1.75 to 2.6
> volts won't matter.
>
> However, if you are using a single 36-volt charger to charge the whole
> string, you may damage the remaining 5 batteries by reducing their
> available finishing voltage by a bit over 0.06 volts per cell. Given
> the voltage range covered by most 36-volt chargers, this is likely a low
> risk. In effect, you're taking 2 volts off the charger voltage for the
> 5 6-volt batteries.
>
> I expect the 8-volt battery will have a lower amp-hour rating (but not
> necessarily). If so, you want to shallow your discharges a bit so you
> don't over-discharge the 8-volt battery while the 6-volters are doing
> fine. You can't trust the single 'fuel gauge' for this. The 8-volter
> is already going to have it reading high, and the 6-volters will happily
> hide the sag in the 8-volter if you are looking at a single volt-meter
> for the string. I think you want a separate meter on the 8-volter, and
> if it reads below 7 volts under load, time to park and charge.
>
> I definitely would not recommend this if the other 5 batteries were
> newish. I'm not convinced it's a good idea even with old batteries.
> However, some days, you need a lash-up to get the job done, even knowing
> it may not be the best idea. My biggest fear here (coming from my
> reality) is that a 'good-enough for today' solution somehow remains in
> effect for a couple of years.
>
> Darryl
>
> On 5/26/2017 2:47 PM, tb wrote:
>> No it wouldn't have the same capacity, but I probably/perhaps don't need
>> it to--just until I can get a 6v. It would cost very little to try, but
>> I don't know if it could damage anything.
>>
>> By the way, it's an E12M--not one of those 'high-tech' big machines.
>> :-)
>>
>> Thanks.
>>
>> Thon
>>
>>
>> On May 26, 2017, at 10:05 AM, David Tiefenbrunn wrote:
>>
>>> I would not do that. The 8v can't have the same capacity as the 6v if
>>> it's is the same size. I free exchange for a used 6v with the other
>>> 5 at end of life isn't a bad idea. Might get you another year.
>>> Definitely not worth getting 1 new one in with the old. It will be
>>> wrecked in short order.
>>>
>>>
>>>
>>> Sent from my Verizon 4G LTE smartphone
>>>
>>>
>>> -------- Original message --------
>>> From: A-M <amcool gbta net <mailto:amcool gbta net>>
>>> Date: 5/25/17 11:58 PM (GMT-05:00)
>>> To: et <Elec-trak cosmos phy tufts edu
>>> <mailto:Elec-trak cosmos phy tufts edu>>
>>> Subject: (ET) 8v battery in the mix?
>>>
>>> My pack is probably 7-10 years old, and still does all I need it
>>> to--or did until I found one battery open circuit this spring.
>>>
>>> As I understand it, putting one new battery in with the other 5 does
>>> no favors to the new guy.
>>>
>>> My local golf cart dealer will basically exchange a 'decent' old
>>> trade-in battery --when he gets one--for my dead one. He's already
>>> been through the spring rush though, so no idea when that might be.
>>>
>>> He does have some trade-in deep cycle 8v batteries though, which seem
>>> to be the same physical size. Any chance adding one to the mix might
>>> not be too much, until a 6v shows up??
>>>
>>> I do have a couple of ICE riders I can use, if this is a bad idea.
>>>
>>> Thanks.
>>>
>>> Thon
>>>
>>>
>>>
>>>
>>>
>>>
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>>
>>
>>
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>
> --
> Darryl McMahon
> Freelance Project Manager (sustainable systems)
>
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