Generator to charge Shimano E8000 battery

Gasser

Member
Feb 6, 2019
39
18
Sidmouth Devon
Hi.
After some advice, would the attached generator be big enough to charge my Shimano E8000 battery’s with the standard chargers

 

jimbob

Active member
Aug 3, 2020
523
433
East UK
More than. My charger doesnt draw above 100W, so thats well upto the task.

It may be a fairly inefficient (read expensive) way of charging though. Not sure of the circumstances where you're looking to use it, but have you thought about a car battery and invertor if only for a quick topup?
 

Gasser

Member
Feb 6, 2019
39
18
Sidmouth Devon
More than. My charger doesnt draw above 100W, so thats well upto the task.

It may be a fairly inefficient (read expensive) way of charging though. Not sure of the circumstances where you're looking to use it, but have you thought about a car battery and invertor if only for a quick topup?
Weekends away emtb but van is multi use, from amazon deliverys (due to lock down) work (sole trader) and leisure, so some times a 3 seater or 6 seater (VW Kombi). So for sleeping I just use a self inflating mattress and Halfords special hob for cooking. So now just after a portable way to recharge the batteries in the evenings before the next day
 

Trig

Member
Sep 23, 2020
78
50
Scotland
Been looking into this myself and was leaning towards an inverter generator also, seemed to be the simplest.

To understand better, and correct me if im wrong... The 100Ah battery mentioned above, if 12v, contains 1200wh? And ive read you lose 20% through the inverters. So 960wh.

So if you have a 625 bike battery, you only get 1 and a half ish charges from that? (Without recharging the leisure battery between)

Do you also need to make any allowances for the amps your charger is? 2A compared to 6A? Or does that only affect how fast it charges from the leisure battery?
 

flash

E*POWAH Elite World Champion
Patreon
Nov 24, 2018
1,050
986
Wamberal, NSW Australia
Been looking into this myself and was leaning towards an inverter generator also, seemed to be the simplest.

To understand better, and correct me if im wrong... The 100Ah battery mentioned above, if 12v, contains 1200wh? And ive read you lose 20% through the inverters. So 960wh.

So if you have a 625 bike battery, you only get 1 and a half ish charges from that? (Without recharging the leisure battery between)

Do you also need to make any allowances for the amps your charger is? 2A compared to 6A? Or does that only affect how fast it charges from the leisure battery?

Yep. Your math is sound. You also need to take into account that AGM batteries only really give you 50% of their rated capacity before you're doing unhealthy discharge. Lithium is more like 80%.Better quality inverters are more efficient.

Here's my system in my Landrover for example: I have a 125aH Lithium battery which gives me 1600 (my batteries are 12.8V nominal) watts total power output hooked up to a high quality 800 watt inverter, which is enough to run my 2.5 amp (at 240V) Shimano charger. The battery is charged while I drive and can also be charged from solar.

So I can get 2 full charges with no charging and three on a day with reasonable sun if I put the panel out. Charging while driving has no impact on my capacity. The whole thing can be removed from the car in 30 seconds and weighs less than a 100aH AGM battery.

A generator will do the same job, much cheaper. I'm just not sure I'd be prepared to have a generator running for three hours to be able to charge a battery. The noise and pollution would be too much for me, personally.

Gordon
 

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