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How rugged are granny chargers for regular use once a week?

4.8K views 5 replies 5 participants last post by  sarahbower1  
#1 ·
I noticed a comment - can't find it now - about a granny charger expiring unexpectedly and so I am interested to know just how rugged these things are. We currently do not have a wall charger at home - not really thought that far ahead as I've only had the car less than 2 weeks.

From what I have found the costs of 7kW chargers after the grant are around ÂŁ600. Even DIY I still need someone to check it and sign it off (and assume they even understand the needs of such beasts anyway)

My current driving is around 100 miles a week and the only way that may change is if we go on trips, in which case I'd use a rapid charger en route.

Thus far I have charged the car twice, once took 14 hours and once 10 hours, the latter being to 100%. (the former was to 86% or so but it got late and I didn't want to leave it overnight being the first time I'd used the charger)

So in reality I only need to charge it once a week and given there are several days that I would not be driving the granny charger is ideal. Economically it makes little sense to me to get a 7kW one installed. Or am I setting it up to meet an early grave by so using it?

(I'm not sold on not getting a 7kW one but it seems a bit of a waste given my usage. Plus I'm from Yorkshire...)
 
#2 ·
The granny charger is a solid piece, no need to worry. Actually there is nothing serious in there, so in case the thing goes south, you can buy another one el cheapo. I use mine 2x-3x a week and it just works. And yes, don't waste your money on the wallbox, since you don't need it, really. The only thing to watch is to avoid charging to 100%: better to stop at 70-80 percent of SoC. Only charge over that if you plan to use the charge in a short while, so SoC will fall below 80 percent quickly.
 
#3 ·
The included granny chargers are pretty solid units. Many owners use them exclusively without issues. In your case with so little weekly mileage, you can easily get by without a L2 charger.

As others have mentioned, best practice for battery longevity would be to charge to 80% most of the time and only go to 100% once every two weeks or once a month (so the cells balance). However, try and arrange that you do this shortly before you plan on doing a drive to bring the SoC down a bit. It's long god for li-ion batteries to be left at a very high SoC (>85%) for long periods (>6 hrs).
 
#4 ·
Thanks for this - and the battery 100% business as well. I had read that on the forum but not really taken it in and did not pick up on it being bad for them to be left at 100% and not used. I've altered the car settings so it will stop at 80% and I can do a 100% charge once a month timed to finish a short time before my work trip. That should keep it happy.
 
#5 ·
Hopefully the Hyundai granny is rugged. But these things have no ventilation, and a very small surface are, so there's a lot of thermal cycling - this is what ages electronic items. They can & do wear out. I used one fairly heavily doing a lot of solar-trickle-charging at 6 to 10A, repaired it when the relays started to fail at 3 years old, and in the 4h year the entire PCB expired, blew apart spectacularly & did >ÂŁ1000 damage to my car. Because it's a compact PCB design, there's nohting separating the 240V from the low-volatge CP signal line, also on the PCB, once the whole thing shorts. Much better to totally isolate the 240V from the low-voltage stuff, but ver hard to do on a PCB base! Modular is better imho.

Chances are with a 1/week use you'll be fine, but these things are really only meant as occasional backup, not for heavy, daily use. For that you really want a much beefier-construction EVSE, with lots of air space, and ideally industrial-grade contactors and modular design. We've seen a few Podpoints with everything on a single PCB fail, and those are almost impossible to repair w/o going back to mfr. Other makes such as Viridian use modular components and industrial off-the-shelf contactors, no custom PCB to lock you in, and these can be easily repaired on a diy basis if you choose.

Details of my saga here: Granny EVSE finally dies - beyond even my zombie efforts...