edit /themes/default-bootstrap/js/cart-summary.js
no Ajax-cart.js and else
here is my develop notes, may help you, use posts in this thred to obtain it, combine oskar86 and karcharoth post
worikg well here PS1.6.0.9
<?
//themes/default-bootstrap/modules/blockcart/blockcart-json.tpl
"totalWeight": {$total_weight|json_encode},{* tcl 2019-04-02 *}
//themes/default-bootstrap/product.tpl
<p >{* tcl 2019-04-02 *}
<label>{l s='Hmotnost:'} </label>
<span class="editable">{round($product->weight,2)} kg</span>
</p>{* konec tcl 2019-04-02 *}
//themes/default-bootstrap/shopping-cart.tpl
<tr class="cart_total_weight">{* tcl 2019-04-02 *}
<td colspan="{$col_span_subtotal}" class="text-right"><span>{l s='Celková hmotnost'}</span></td>
<td colspan="2" class="price"><span id="total_weight">{$cart->getTotalWeight()|escape:'htmlall':'UTF-8'|number_format:3} {Configuration::get('PS_WEIGHT_UNIT')}</span></td>{* konec tcl 2019-04-02 *}
</tr>
<td rowspan="{3+$total_discounts_num+$use_show_taxes+$total_wrapping_taxes_num+1} " colspan="2" id="cart_voucher"class="cart_voucher">
<td rowspan="{3+$total_discounts_num+$use_show_taxes+$total_wrapping_taxes_num+1} {* tcl 2019-04-02 *}" colspan="2" id="cart_voucher" class="cart_voucher">
//classes/Cart.php
$total_weight = $this->getTotalWeight();
'total_weight' => $total_weight.' '.Configuration::get('PS_WEIGHT_UNIT') /*tcl*/
//themes/default-bootstrap/js/cart-summary.js
$('#total_weight').html(json.total_weight); /*tcl*/