geem
Well-Known Member
Also, lithium bms SOC values are notoriously in accurate. We have those but still use a Smart shunt
Non-bluetooth lifepo battery for trolling motor
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Allan
Well-Known Member
I hope it's OK to restart this post. I've been looking at trolling motors for our dinghies. The battery and it's charging are my sticking point at present. I've decided that knowing how much power we have is quite important and although a little heavy the Eco-Worthy 100Ah seems to fit the bill (12V 100Ah LiFePO4 Lithium Battery with Bluetooth | Deep Cycle & 10-Year Life). I'm thinking of just fitting it with a suitable Anderson plug/socket for the motor and then having another to charge it connected directly to our three x 110Ah domestic bank. We have charging from a Marlec controller fed by a Rutland wind powered generator, a Victron MPPT 75/15 fed by 4 x 50 PV panels and the engine alternator. Our domestics normally range from 12.5v to 13.8v depending on wind, sun or motoring. We run our fridge 24/7 and never have to run the engine just for charging.
Does this seem like an acceptable solution?
Allan
Does this seem like an acceptable solution?
Allan
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mjcp
Well-Known Member
I have a DC House 12V 100Ah LiFePo4 battery for my dinghy, I don't worry about the State of Charge - I never ran low when using the 100Ah Lead acid, so the same capacity of LiFePo4 gives me 4 x the capacity in useable terms.
I charge when ashore, but could use the shore power if available.
I stick a bag for life over the top to keep the splashes off it, mine is the one with a USB socket etc on top, base water proof but not the gubbins on top!
In terms of wight - I could lift the lead acid onboard, but not fun.... the new one is *way* easier!
I charge when ashore, but could use the shore power if available.
I stick a bag for life over the top to keep the splashes off it, mine is the one with a USB socket etc on top, base water proof but not the gubbins on top!
In terms of wight - I could lift the lead acid onboard, but not fun.... the new one is *way* easier!
Allan
Well-Known Member
Many thanks that's interesting. The battery I have in mind simply has terminals on top so I don't think a box will be required. Can you please explain why you now have 4 X the capacity?
Allan
Refueler
Well-Known Member
I was also going to ask about the 4x .... as its about 1.8x in reality - if you take max safe discharge level of lead acid.
Refueler
Well-Known Member
Question to you guys :
Given that prior to LiFePo4 price drop / availability etc ... people tootled along with plain Lead Acid ... learnt to adjust their use based on time / usable capacity ...
Is it really any different now with LiFePo4 ??
I have a 100AH with BT .... great - but my Samsung Phone refuses to get data from it .. but all my other tablets do ....
I have a 20AH without BT .... do I miss BT ? No.
Given that prior to LiFePo4 price drop / availability etc ... people tootled along with plain Lead Acid ... learnt to adjust their use based on time / usable capacity ...
Is it really any different now with LiFePo4 ??
I have a 100AH with BT .... great - but my Samsung Phone refuses to get data from it .. but all my other tablets do ....
I have a 20AH without BT .... do I miss BT ? No.
mjcp
Well-Known Member
Old Lead acid - 100Ah = 20Ah of usable capacity (avoiding over discharge),
New LiFePo4 - 100Ah = 80Ah of usable capacity.
20 x 4 = 80, so 4 times.
M
Sea Change
Well-Known Member
That's very conservative. Most people would take a lead acid down to 50% without worrying.
Yes, they will last longer if you only take them to 80%, but it's all a sliding scale.
Trojan published a chart of life cycles vs depth of discharge, which showed that you got essentially the same Ah in total from the batteries whether you discharged to 80% or 50%. So buying a bigger bank and only mildly discharging will last longer, but you could also buy a smaller bank, discharge it a bit deeper, and replace it sooner. Overall life cycle cost is the same.
wingcommander
Well-Known Member
Indicating your old lead acid was well into its final stage of life ... get ya
wingcommander
Well-Known Member
Think opp suggests his old l/a battery, held a lot less due to age . Bit like me really
mogmog2
Well-Known Member
We do pretty much this. Except we're still running a 25Ah agm. We have 2 x 50W rigid panels in parallel, compressor fridge, wind gen all into a single 110Ah (could do with a little bit more generation and battery TBH, but we're only just short if it's cloudy etc) but we cruise fully ofc grid ok. So your 4 panels plus bigger batteries will be a big leap. FWIW, I bought the little battery to see what it would do - it had to get us ashore and back say at East Head or Newtown and it does that easily (but not quickly - quicker than rowing though
). When this one dies, I'll look at lithium, but this is working for us ATM. AFAIC, it's all very well having a Torqeedo and bombing around like Crockett and Tubbs, but you've got to find that energy from somewhere when you get back - and it's not going to be shore power for us, so we go leisurely instead 
And I've just taken delivery of a Victron smartshunt so I can (a) monitor the battery in real time (b) see how much we need to put back in and (c) monitor overall use over time and as part of the boat's energy budget - which is why I paid extra for Victron
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